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(define-module (hnh util values)
:use-module (ice-9 control)
:export (abort* on-fst on-snd apply/values)
)
(define-syntax-rule (abort* form)
(call-with-values (lambda () form) abort))
;; (on-fst (+ 2 (abort* (values 3 4))))
;; ⇒ 5 ⇒ 4
(define-syntax-rule (on-fst form)
(% form
(lambda (prompt fst . rest)
(apply values (prompt fst) rest))))
(define-syntax-rule (on-snd form)
(% form
(lambda (prompt fst snd . rest)
(apply values fst (prompt snd) rest))))
(define-syntax-rule (apply/values proc form)
(call-with-values (lambda () form)
proc))
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